adjective

having or showing care and conscientiousness in one’s work or duties.

after diligent searching, he found a parcel

industrious,hard-working,assiduous,conscientious,particular,punctilious,meticulous,painstaking,rigorous,exacting,careful,thorough,sedulous,attentive,heedful,intent,earnest,studious,constant,persevering,persistent,tenacious,pertinacious,zealous,dedicated,committed,driven,active,busy,unflagging,untiring,tireless,indefatigable,dogged,plodding,slogging,laborious